SAB80C517-M16 SIEMENS [Siemens Semiconductor Group], SAB80C517-M16 Datasheet - Page 15

• Manufacturer Part Number: SAB80C517-M16
• Description: 8-Bit CMOS Single-Chip Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

4
The SAB 80C517 CPU manipulates operands in the following four address spaces:
4.1
The program memory of the SAB 80C517 consists of an internal and an external memory portion
(see figure 4-1). 8 Kbytes of program memory may reside on-chip (SAB 80C517 only), while the
SAB 80C537 has no internal ROM. The program memory can be externally expanded up to
64 Kbyte. lf the EA pin is held high, the SAB 80C517 executes out of the internal program memory
unless the address exceeds 1 FFF H . Locations 2000 H through 0FFFF H are then fetched from the
external program memory. lf the EA pin is held low, the SAB 80C517 fetches all instructions from
the external program memory. Since the SAB 80C537 has no internal program memory, pin EA
must be tied low when using this device. In either case, the 16-bit program counter is the addressing
mechanism.
Locations 03 H through 93 H in the program memory are used by interrupt service routines.
4.2
The data memory address space consists of an internal and an external memory portion.
Internal Data Memory
The internal data memory address space is divided into three physically separate and distinct
blocks: the lower 128 byte of RAM, the upper RAM area, and the 128-byte special function register
(SFR) area (see figure 4-2). While the latter SFR area and the upper RAM area share the same
address locations, they must be accessed through different addressing modes. The map in
figure 4-2 and the following table show the addressing modes used for the different RAM/SFR
spaces.
Semiconductor Group
– up to 64 Kbyte of program memory
– up to 64 Kbyte of external data memory
– 256 bytes of internal data memory
– a 128-byte special function register area
Program Memory
Data Memory
Memory Organization
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Memory Organization